Illumination devices (e.g., lamps) that comprise light emitting diodes (LEDs) as luminescent components usually cannot simply be connected to a voltage supply but have to be driven by special driver circuits (or control circuits) providing a defined load current to the LEDs in order to provide a desired radiant power (radiant flux). Since a single LED exhibits only small forward voltages (from about 1.5 V for infrared GaAs LEDs ranging up to 4 V for violet and ultraviolet InGaN LEDs) compared to commonly used supply voltages (for example, 12 V, 24 V and 42 V in automotive applications) several LEDs are typically connected in series to form so-called LED chains.
LEDs are current-driven components and that typically employ driver circuits including a load current regulation. In order to reduce power dissipation within the driver circuits, switched-mode power supplies are usually employed to supply an LED or LED chain with a well-defined load current.